Electrolytic recovery of zinc and manganese.



I UNITED strArns raTENT OFFICE.

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ELECTROLYTIC, RECOVERY OF ZINC AND MANGANESE.

Patented Mar. 4, 1913.

No Drawing. Original application flied September a, 1912, Serial No. 718,508. Divided and this application flied February 4, 1913. Serial No. 748,121.

To all whom it may concern Be it known that I, ANDREW GORDON FRENCH, a citizen of the Dominion of (Jan- -ada, resident of Nelson, in the Province of British Columbia, Canada, have invented certain new' and useful Improvements in Electrolytic Recovery of Zinc and Manganese, of which the following is a specification.

This invention relates to a process for the recovery of metallic zinc and manganese 'dioxid by electrolysis, the object bem to recover these materials in a dense, pure orm in the case of zinc, and in a pure marketable condition in the case of the manganese dioxid. It forms part of a treatment for the recovery of these materials from refractory complex zinc-lead ores containing manganese. The preparatory treatment of these ores is set forth in my Patent #1,041,060 of October 15, 1912. In the process set forth in that application the final result was a strong, aqueous solution of sulfate of zinc with neutral sulfate of sodium and containing more or less sulfate of manganese, which is usually present in the complex ores which this process is designed to treat. These three salts, when in solution together, are easily split up by a low voltage direct electric current and yields on the cathode a dense deposit of very pure, metallic zinc and i on the anode pure manganese dioxid. It is on the favorable combination of these three salts that the success of this process do ends and where the manganese is not in su cient quantity to form that favorable combination, this element should be added in order to obtain the most satisfactory results.

The following specification fully describes the process as conducted.'

The aqueous solution of the sulfates of zinc and manganese wit-h neutral sulfate of sodium is delivered into an electrolytic tank having lead anodes and thin, sheet zinc cathodes and a direct current of from two and a half to four and a half volts with a current density of from twenty to thirty amperes per square foot of cathode surface is passed through the solution. Under this current a very pure metallic zinc is formed as a dense deposit on the cathodes and pure manganese dioxid at the anodes. The purit; of the zinc, particularly in its absolute freedom from oxid of zinc and sulfur compounds, the presence of which in previous attempts at electrolytic recovery have caused sponginess and deterioration of the deposit, is attributable chiefly to the association with the zinc in the electrolyte of the manganese and. sodium sulfates. These three salts in solution together, when crystallized out do so as a triple salt. A further advantageous feature of this treatment lies in the fact that the sulfuric acid which is liberted from the zinc and man anese sulfates combines in its nascent con ition with the neutral sulfate of sodium to form bisulfate and persulfate of sodium in the electrolite, and as these reactions are exothermic t e'current is correspondingly reinforced. A second reinforcement ina similar manner is obtained from the formation of the manganese dioxid at the anode.

In the practice of the process, the solution, which forms the electrolyte, is madeto flow continuously from the ore leaching tanks into the electrolytic tank, in a nearly saturated condition and free from acidity, andfzfireturn flow of the electrolyte, after havlng been partially acted upon by the current, 1s returned from the electrolytic tank to the ore leaching tank. A proportion of the zinc and the manganese having been abstracted from the solution and de osited respectively on the cathodes and at t e anodes, the return flow of the solution to the leaching tank is in an acid condition, having from one and a half to two and a half, or cent. of acidity asbisulfate and persul ate of sodium. This acidity enables it to dissolve out a fresh supply of zinc and manganese in the leaching tank, and this process is continued until the ore in the leaching tank is depleted of its zinc and manganese.

As described in the preamble, when treating solutions from ores which are poor in manganese, it is necessary to mix it with others richer inthat element so as to give one unit of manganese to from four to six units of zinc, which I find to be a good working proportion, although if a greater proportion of manganese be employed the operation may still be successfully performed. In circumstances where ores sufficiently rich in manganese are not obtainable, I obtain the required sulfate of manganese by treating a proportion of the manganese dioxid mud as deposited at the anodes with sulfurous acid gas, either free or in solution, while the dioxld is carried in as small a quantity of water as will hold it in suspension. This immediately takes oxygen from the dioxid forming the soluble manganese sulfate which is required'to add to the electrolyte.

The sulfurousacid may be obtained from the fluesof the furnace used for calcining the sulfid ores in the earlier treatment R ferred to, as being the subject of the Patent #1,0 l1,060 hereinbefore referred to.

The process here described. is advantageous in that it produces a particularly dense and pure form of metallic zinc, and similarly the dioxid of manganese is commercially pure, and these results are obtained with a very low voltage current owing to the electrolyte being a solution of the three salts above referred toand to the I fact that the reactions in the electrolytic tank are exothermic reinforcing the cur rent. Y I

While I have described herein the complete process I do not broadly claim the same in this applicat1on, n0r do I claim the species ofthe process which has relation to the treatmentof ores that contain plenty of manganese, as such forms the subject matter of my original application filed September 4, 1912 #718,506, of which this application is a divisional part, and hasparticular relation to the process as employed in connection with ores which are not sufficiently rich in manganese but require the regeneration suspension in water by sulfurous acid gas or a sulfurous acid solution.

2. A process for the recovery of pure metallic zinc and manganese dioxid which comprises the electrolytic decomposition of a solution containing sulfate of zinc, sulfate of manganese" and neutral sulfate of sodium,

the electrolyte after being acted upon'being treated 'toeffect the regeneration of the required sulfate ofmanganese by treating dioxid of manganese in suspension by sulfurous ac1d gas'or a sulfurous acid solution,

and then delivering the electrolyte after being regenerated to the leaching tank from which the original supply was obtained and replaced in the electrolytic tank by'a supply drawn from the same leachin tank. ANDREW GORDON? FRENCH. Witnesses ALBERT E. DIETERIGH, G120. B. Prr'rs. 

